A dry shaver having a rockable head is known. The rocking of the shaver head facilitates good contact between the shaver head and the user's skin during shaving.
WO 93/12916 (U.S. Pat. No. 6,098,289 (Wetzel et al.)) discloses a shaver having a head rockably mounted on a shaver body by means of first and second linkage mechanisms at respective ends of the head. Each linkage mechanism comprises a pair of transverse link members and a pair of vertical link arms pivotally mounted on the head and depending therefrom. Each arm is mounted on the shaver body by means of the transverse link members pivotably attached to the link arms at respective ends and to the shaver body at a central pivot axis lying in a common plane of symmetry of the first and second linkage mechanisms. The resulting four-bar linkage permits the head to rock about a virtual pivot axis located above its points of physical attachment to the link arms. This arrangement is a symmetric parallelogram, with the congruent pivot locations all lying in parallel lines.
Further linkage mechanisms of this type are described in U.S. Pat. Nos. 5,704,126 (Franke et al.), 5,159,755 (Jestädt et al.) and U.S. Pat. No. 4,797,997 (Packham et al.).
It is known in the field of dry shavers, e.g. in those distributed widely in the United States and Europe by the company Braun GmbH under the trade designations “Flex Integral” or “Synchro”, to have the shaving head mounted on a pin bearing defining a pivot axis about which the head travels in an arc of about +/−24 degrees either side of a rest position.
Four bar linkages have also been proposed to generate a virtual pivot axis and/or a side-to-side swivel axis in wet razors as in U.S. Pat. No. 6,115,924 (Oldroyd). Reference may also be made to GB-A-1,460,732 (Terry et al.) which discloses a four bar box-like structure arranged parallel to the longitudinal axis of the cutting head of a wet razor.
Other four-bar linkages in wet razors are known from U.S. Pat. No. 5,535,518 (Althaus), which purports to describe a parallelogram linkage in which each of two transverse links can buckle at a bend joint to unload a wet razor cartridge, and from U.S. Pat. No. 5,953,824 (Ferraro et al.), which discloses a linkage whose longitudinal arms have slots which are cammed by motion relative to fixed pins on the housing as the base transverse link rocks from side to side, in order allegedly to maintain a relatively constant distance between the razor head mounting pins.
As mentioned above, an advantage of the four bar linkage mechanism of the type known from WO 93/12916 is that, as described in more detail hereinafter, a virtual pivot centre may be produced well above the points of attachment of the vertical side members to the shaving head. In fact, the virtual pivot may be located above, at or even below skin level, in dependence upon the height of the transverse link members, typically in the form of pivoting triangles or bell crank links. This may be achieved without the need for a physical upper pivot location. However, a disadvantage of the mechanism is that the two vertical side members have to be arranged essentially parallel to the vertical plane of symmetry of the mechanism. In other words, the three points of attachment of each arm to, respectively, the rocking head, the first transverse link member and the second transverse link member lie on a straight line parallel to the plane of symmetry. Applicant has recognized that the resulting mechanism is relatively bulky and cannot be accommodated in a slim housing.